Functional Features of Nociceptive-Induced Suppression of Alpha Band Electroencephalographic Oscillations

Nociceptive stimuli can induce a transient suppression of electroencephalographic oscillations in the alpha frequency band (ie, alpha event-related desynchronization, alpha-ERD). Here we investigated whether alpha-ERD could be functionally distinguished in 2 temporally and spatially segregated subcomponents as suggested by previous studies. In addition, we tested whether the degree of dependence of nociceptive-induced alpha-ERD magnitude on the prestimulus cc-power would have been larger than the degree of dependence on the poststimulus cc-power. Our findings confirmed the dissociation between a sensory-related alpha-ERD maximally distributed over contralateral central electrodes, and a task-related alpha-ERD (possibly affected by motor-related activity), maximally distributed at posterior parietal and occipital electrodes. The cortical sources of these activities were estimated to be located at the level of sensorimotor and bilateral occipital cortices, respectively. Importantly, the time course of the alpha-ERD revealed that functional segregation emerged only at late latencies (400 to 750 ms) whereas topographic similarity was observed at earlier latencies (250 to 350 ms). Furthermore, the nociceptive-induced alpha-ERD magnitude was significantly more dependent on prestimulus than poststimulus cc-power. Altogether these findings provide direct evidence that the nociceptive-induced alpha-ERD reflects the summation of sensory-related and task-related cortical processes, and that prestimulus fluctuations can remarkably influence the non-phase-locked nociceptive alpha-ERD. Perspective: Present results extend the functional understanding of cc-oscillation suppression during pain perception and demonstrate the influence of prestimulus variability on this cortical phenomenon. This work has the potential to guide pain clinicians in a more accurate interpretation on physiological and psychological modulations of alpha-oscillations. (C) 2013 by the American Pain Society